The present invention relates to toners and development systems for toners.
Digital printers and similar products provide documents that are frequently finished into booklets or folded for mailing in post printing finishing equipment. While the advancement of toners and development systems has been significant, there is still a need to improve the fusing quality of the toner image so that the toner does not smear or xe2x80x9cruboffxe2x80x9d in friction fed finishing equipment which could lead to a gray or black smear on the sheet. Also, the toner image, if the proper properties are not present, may noticeably crack when a paper sheet is folded. While many toner fusing systems have excellent image quality, for example, dark solid blacks, the ruboff can be improved. Accordingly, there is a need to provide a process that produces prints with high image and fusing quality thus avoiding the above-described disadvantages.
A feature of the present invention is to provide a development system which provides a printed image having sharp image quality and excellent fusing quality.
Another feature of the present invention is to provide a toner using a development system which provides prints with high image quality and fusing quality.
A further feature of the present invention is to provide methods to reduce ruboff of a printed image and yet maintain image quality.
Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the written description and appended claims.
To achieve these and other advantages and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention relates to a development system for toners. The development system includes a supply of dry developer mixture which contains toner particles and hard magnetic carrier particles. The development system further includes a non-magnetic, cylindrical shell for transporting the developer between the supply and the development zone wherein the shell can be rotatable or stationary. A rotating magnetic core of a pre-selected magnetic field strength and means for rotating at least the magnetic core to provide for the transport of the toner particles from the shell to an electrostatic image are also provided as part of the development system. The development system further includes a fusing roll coated with silicone rubber or other low surface energy elastomers or resins. Preferably, the fusing roll is a filled silicone rubber fusing roller.
The toner used in the development system is preferably a toner containing at least one toner resin, at least one release agent, at least one surface treatment agent, and optionally at least one colorant and/or at least one charge control agent.
The present invention further relates to a method for developing an electrostatic image with the above-described toner. The method involves developing an electrostatic image member bearing an electrostatic image pattern by moving the image member through a development zone and transporting developer through the development zone in developing relation with the charge pattern of the moving imaging member by rotating an alternating-pole magnetic core of a pre-selected magnetic field strength within an outer non-magnetic shell, which can be rotating or stationary, and controlling the directions and speeds of the core and optionally the shell rotations so that developer flows through the development zone in a direction co-current with the image member movement, wherein an electrographic two-component dry developer composition is preferably used. The method further involves transferring the toner to a substrate and the substrate with the toner image is then subsequently fused by passing the toner image on the substrate through a fusing roll to fuse the image on the substrate wherein the fusing roll is a silicone rubber coated fusing roller or is coated with other low surface energy elastomers or resins. The fuser roll is preferably in a pressure contact arrangement with a backup or pressure roll. The dry developer composition contains charged toner particles and oppositely charged carrier particles. Preferably, the carrier particles are a hard magnetic material exhibiting a coercivity of at least about 300 gauss when magnetically saturated and also exhibit an induced magnetic moment of at least about 20 EMU/gm when in an externally applied field of 1,000 gauss. The carrier particles have a sufficient magnetic moment to prevent the carrier particles from transferring to the electrostatic image.
The present invention also relates to a developer which contains the above-described toner particles with hard magnetic carrier particles.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the present invention, as claimed.